The constants include integers such as

0 1 999 -512

Besides the usual decimal, or base 10, notation, integers may also be
written in other base notations. In `sicstus`

mode, any base from
2 to 36 can be specified, while in `iso`

mode bases 2 (binary), 8 (octal),
and 16 (hex) can be used. Letters `A`

through
`Z`

(upper or lower case) are used for bases greater than 10. E.g.:

15 2'1111 8'17 16'f % sicstus mode 15 0b1111 0o17 0xf % iso mode

all represent the integer fifteen. Except for the first, decimal,
notation, the forms in the first line are only acceptable in
`sicstus`

mode, while those in the second line are only valid in
`iso`

mode.

There is also a special notation for character constants. E.g.:

0'A 0'\x41 0'\101

are all equivalent to `65`

(the character code for `A`

).
`0'`

followed by any character except `\`

(backslash) is thus
read as an integer. Unless character escapes have been switched off, if
`0'`

is followed by `\`

, the `\`

denotes the start of an
escape sequence with special meaning (see Escape Sequences).